Method of bleaching



/ Temp ant Cami tiODlFl- Q-MlON t l'EXl'lLES ti HEW-$1 1 E Patented Dec. 25, 1945 UNITED STATES tact Room METHOD OF BLEACHIN G Hans 0. Kauffmann, Eggertsville, and Paul H. Margulies, Kenmore, N. Y., assignors to Buffalo Electro-Chemical Company, Inc., Buffalo, N. Y.

No Drawing. Application May 19, 1939, Serial No. 274,650

1 Claim.

The present invention relates to a method of bleaching goods composed of fibers of cellulose, regenerated cellulose, and artificial silks that contain colored portions dyed with so-called naphthol and related dyes, and like colors normally not fast to active oxygen bleachin solutions, by the employment of bleaching solutions containing hydrogen peroxide or other materials of the peroxide and percompound group that generate active oxygen.

It has been recognized heretofore that in bleaching goods containing colored striped portions, those goods dyed with certain types of dyes, notably the naphthol dyes, could not be bleached in conjunction with other goods, whether plain white or colored, due to the fact that a portion of the dye was liberated during the bleachin and stained a considerable portion of the goods being bleached. Further, the dye would crock or transfer to other goods by contact or abrasion.

Furthermore, even where goods of the class specified and containing colored portion dyed with naphthol dyes were bleached heretofore, much dye was washed out in the bleaching operation, probably in a purely mechanical fashion, and colored the other portions and p rticular y those portions not containing any dye. This necessitated laborious after-treatment and continued washing to remove the color that had been taken up by the goods. As the naphthol dyes, particularly, were not wash and launder fast, bleeding and washing out Was encountered when such goods were treated with soap and other detergent solutions.

For this reason goods containing colored portions dyed with naphthol dyes had to be bleached carefully and in a particular manner and by the employment of special machinery. The goods were carefully and continuously moved through the bleaching solution, squeezed out and washed to prevent deposition of washed out dye and prevent staining. Even with repeated treatments of the goods with bleaching solutions, a good white in the uncolored portions of the goods was not obtained. Special chlorine bleach baths Were required for bleaching naphthol dyed goods and the latter required special handling to prevent crocking of the dye. Due to the special and re.. peated handling, much chlorine was consumed; further the pattern was often pulled out of shape. As a result of such prior treatments, the dyed portions often were rusty and dull in appearance.

The present invention provides a method of bleaching goods composed of cellulose, regenerated cellulose, and artificial silk, or any of them, that contain colored portions dyed with napt-hol dyes, in conjunction with undyed goods and goods containing portions dyed with other classes of dyes.

The present invention also provides a bleaching procedure whereby goods of the class specified can be bleached with other goods, as, for instance, wool and the like.

The present invention also provides a method of bleaching goods of the type specified wherein the wash fastness of the dye is increased and the washing out of the dye in subsequent laundering operations substantially eliminated.

The present invention also provides a method of treatin goods of the type specified wherein c'rocking is eliminated, thus permitting bleaching and subsequent laundering of goods dyed with naphthol dyes and the like, in conjunction with undyed goods and goods dyed with other classes of dyes. i

The present invention, therefore, provides a method for the production of goods dyed with naphthol dyes wherein the dye appears to be fixed upon the fibers.

The present invention also provides a method for producing goods of the class specified wherein the naphthol dye retains its original shade, brilliance and luster and is not rusty and dull.

In accordance with the present invention, goods containing fibers of cellulosic material, regenerated cellulose, artificial silk, or any of them, are treated at elevated temperatures with solutions containing active oxygen generating materials at pHs of below about 9.0. In bleaching goods of the type specified the active oxygen generatin agent preferred is hydrogen peroxide, although the peroxides and percompounds generally may be employed, as, for instance, alkali metal peroxides and alkaline earth metal peroxides, other metal peroxides, perborates, percarbonates, persilicates, and the like, designated herein as peroxides or active oxygen compounds. The peroxide bath is stabilized, preferably with a soluble silicate, such as sodium silicate, although other stabilizers may be substituted therefor. In contrast with the conventional peroxide bleach for colored goods having a tendency to bleed or mark oif, wherein the temperature of treatment is about -170 F., the temperature of the bleaching bath as employed in the present invention, and therefore the temperature of treatment, is above about F. and may be 212 F. and higher.

Care must be taken that the hydrogen ion concentration be controlled and the pH value of the solution be below about 9.0; in the preferred operation of the present invention, the pH of the treating bath is adjusted initially to about 8.7 to 9.0 and the pH permitted to drop slowly during the bleaching. At the end of about six to ten hours, it will be found that the pH of the solution has dropped to about 6.8 to 7.8.

In an alternative procedure the initial pH can be adjusted to about 8.0 or somewhat below 8.0, say 7.8, and maintained at substantially the ini tial value during the treatment and in any event to below about 8.0.

Where necessary, the goods may be subjected to a plurality of such treatments in order to obtain the degree of whiteness desired in the undyed portions. The time of treatment, the temperature of the bleach bath, the composition of the bath, and concentration of the bleaching agent therein, will depend upon the type of goods being treated and the degree of white desired. In general, it may be stated that the bleachin operation must be carried out by maintaining contact of goods with the solution for from about two hours to ten hours at temperatures above 180 F., preferably by circulating the heated bleaching solution over and through the goods.

The means employed for maintaining the pH value within the range about 6.5 to 9.0 may be any suitable means not damaging the fibers. As bleaching proceeds, the pH will drop slowly and the end pH should be above about 6.5. Where hydrogen peroxide bleaching solutions are employed, a soluble silicate may be added thereto in amount sufiicient to produce the desired pH. Employment of even one-half cc. of 40 B. silicate per liter may give the result desired. However, the bleaching effect desired is not economically obtained under such conditions due to the instability of the bath. Where the pH is raised above the critical range pH 9.0-9.5 by using higher amounts of silicate or other alkali to obtain better stability, bleeding of the dye is initiated although good bleached effects may be obtained. However, under these conditions bleeding can be prevented by including a dye conditioning agent in this bath.

But such dyes are not fast on subsequent treatment, as for instance laundering, or they change in shade.

In accordance with the present invention, a material designated as a dye conditioning agent is included in the bleach bath for the purpose of preventing staining of the fiber by crocking or by dye that has washed out of the goods. The dye conditioning agent is a surface active material substantially insoluble in the solution, or a material capable of producing latent alkalinity therein, or both. It has been found, in accordance with the present invention, that soluble magnesium salts, as, for instance, epsom salts, are excellent dye conditioning agents and when incorporated in the bleach bath, in conjunction with soluble silicate as a stabilizer, apparently react with the stabilizer and produce in the bath a relatively insoluble material which, however, is capable of providing a considerable quantity of latent alkalinity. Although the real function and operation of the soluble magnesium salt is not known at this time, it is believed that either a mechanical or chemical effect, or both, is exerted by the added magnesium salt upon the dye. These elfects, at the pH employed, condition the dye already present on the fiber so that the dye is fixed and retained thereon and is not removed by crocking, abrasion, or washing.

Other dye conditioning agents are salts or metals which at a pH of about 9.0 and below form precipitates partially or wholly insoluble under the stated conditions. The precipitates comprise hydrated oxides, hydroxides, silicates, and the like, of the metal employed. Thus soluble zinc or aluminum salts are excellent for this purpose,

as are magnesium oxide, aluminum hydroxide,

In carrying out the bleaching procedure, as well as any preliminary treatments, it is suggested that if iron kiers be used, only those be employed that are rust free and have good linings. Furthermore the presence of well known catalysts in the peroxide bath or on the goods should be avoided or rendered inactive especially in this instance where the bleaching is performed under conditions of low pH.

As a specific example of the procedure, purely illustrative but not definitive thereof, lbs. of red bordered toweling dyedwith a naphthol dye were treated at 212 F. for six hours in 50 gallons of bleaching solution containing Pounds Epsom salts 1.2 Sodium silicate, 40 B 1.5 Hydrogen peroxide-100 volume 1.33

The initial pH was 8.7; the final pH 7.3. The bleaching solution contained a heavy flocculus and colloidal precipitate, contained no color and the goods presented a clear definition between the red colored portions and the uncolored portions. In order to obtain a full white, the goods were again subjected to a bleach bath containing in 50 gallons,

Pounds Epsom salts 1.2 Silicate, 40 B 1.66 Hydrogen peroxide-400 volume 2 The initial pH was 9.3 and the final pH 6.5. At the end of eight hours the goods were removed and rinsed and found to be completely bleached, contained no crock marks and no dye washed or bled into the undyed portions. The temperature of the second treatment was F.

Where desired, and where the dye permits, the colored goods may be first boiled in a suitable alkaline solution and it has been found that a solution containing 50 lbs. soda ash and 5 lbs. of soap in 1000 gallons of water gives an excellent alkaline boiling medium for the treatment of goods containing color portions dyed with naphthol dyes.

In a variation of the present invention, goods that may be stained with dye marks and the like produced by bleeding, crocking, or otherwise, may be treated at a pH below about pH 9 with a peroxide bleaching bath containing a dye conditioning agent. Upon heating the goods in such a bath the stains and dye marks are removed and clean bleached goods obtained.

It will be understood that the use of the usual wetting out agents and the like ma be employed in conjunction with the process of the present invention and such use is included within the scope of the present invention.

The term goods, as used herein, includes raw stock as well as spun and carded materials, yarn, and knitted and woven goods.

We claim:

The method of bleaching goods composed of fibers of the class consisting of cellulose, regenerated cellulose, and artificial silks, and which contain portions dyed with naphthol dyes, which comprises treating the goods with an alkaline active oxygen bleaching solution having an initial pH value of less than about 9.0 and containing a freshly precipitated magnesium compound possessing latent alkalinity suspended therein in amount sufficient to render dye fast to active oxygen bleaching solutions.

HANS O. KAUFFMANN. PAUL H. MARGULIES. 

